A light-emitting diode (LED) is a semiconductor light emitter used as a light source in a variety of applications, such as display lights, warning lights, indicator lights, or other applications where white or colored light is desired. The color of light produced by an LED is determined, at least in part, by the type of semiconducting material used in its manufacture. For LEDs used in general illumination applications (e.g., general or ambient lighting), the emission spectrum (i.e., intensity of light versus its wavelength) may be the result of a compromise between a preferred color point and color rendition (the effect of a light source on the color appearance of objects and an aspect of color quality) on the one hand, and (luminous) efficacy on the other hand, due to the limitations of practical emitter and converter materials.
In an example, existing LED designs for outdoor and industrial applications often prioritize efficacy over color quality because such applications typically have long operating hours providing potential to exploit significant energy savings, and often do not need high color fidelity. These characteristics, associated with outdoor and industrial applications, have led to a prevalence of LEDs with cool-white and neutral-white correlated color temperatures (CCT) (e.g., CCT values of 4000 Kelvin (K) and above) with moderate color rendering index (CRI) (CRI is a scale from 0 to 100 percent indicating how accurate a given light source is at rendering color when compared to a “reference” light source). An example of a cool-white LED with moderate CRI is a 4000K/70 LED with CCT equal to 4000K and a CRI value of 70. The emission spectra associated with such existing LEDs as the 4000K/70 LED have significantly more blue spectral content than some of the incumbent technologies that they replace (e.g., high-pressure sodium lighting), which has caused recent concerns about their impact on human physiology, and in particular circadian rhythms.